American Association for Aerosol Research - Abstract Submission

AAAR 37th Annual Conference
October 14 - October 18, 2019
Oregon Convention Center
Portland, Oregon, USA

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Characterizing Aerosol Emissions from Wildfires in the Western US

EZRA LEVIN, Kevin Barry, Kathryn Moore, John Ortega, Lauren Garofalo, Matson A. Pothier, Darin Toohey, Mike Reeves, Jakob Lindaas, Ethan Emerson, Delphine K. Farmer, Sonia Kreidenweis, Paul DeMott, Emily Fischer, Colorado State University

     Abstract Number: 536
     Working Group: Biomass Combustion: Emissions, Chemistry, Air Quality, Climate, and Human Health

Abstract
Wildfires are a major source of fine and accumulation mode aerosol in the western United States, especially during the summer months. Increased fire activity has been observed in recent years and wildfires are predicted to become even larger and more numerous under future climate scenarios. Emissions from wildfires increase aerosol number and mass concentrations locally and can also be transported over long distances, leading to regionally elevated aerosol loadings. Because of their high concentrations, these emissions can have a significant impact on local air quality and visibility reduction, as well as global radiative balance and can also affect cloud and precipitation formation by increasing the number of available cloud nuclei. To better understand wildfire aerosol emissions in the western US, we sampled numerous smoke plumes with a comprehensive suite of aerosol and gas phase instruments onboard the NSF/NCAR C-130 as part of the Western Wildfire Experiment for Cloud Chemistry, Aerosol, Absorption and Nitrogen (WE-CAN) study during the summer of 2018. Here we present aerosol size distributions across a wide diameter range (~10 nm – 3 µm) from combined measurements from a Nano Scanning Mobility Particle Sizer (NSMPS), two Ultra High Sensitivity Aerosol Spectrometers (UHSAS) and a Passive Cavity Aerosol Spectrometer Probe (PCASP). We also present mass and number concentration and mixing state of refractory black carbon (rBC) measured with a Single Particle Soot Photometer (SP2), and concentrations of cloud condensation nuclei (CCN) and derived aerosol hygroscopicity measured with a CCN counter. Overall, wildfire aerosol emissions were found to be dominated by accumulation mode particles, with geometric mean diameters between 150 – 250 nm. Black carbon particles were mostly thickly coated, likely by organic components, and aerosol hygroscopicity was generally very low.